The present invention relates to a device and a method for determining the dirt load in a rinsing or detergent solution in a water-conducting household appliance, e.g. in a dishwasher. The invention further relates to a water-conducting household appliance incorporating such a device. The invention also relates to methods for cleaning wash items in a water-conducting household appliance and to the use of detergent product formats in combination with the methods described here.
In water-conducting household appliances such as dishwashers, for example, it is possible to react to differences in respect of the quantity and kinetics of the dirt load in the rinsing or detergent solution, which correlates with the soiling of the wash items, with the aid of sensors, in particular optical sensors, which typically measure the turbidity of the rinsing or detergent solution. The wash parameters can be adjusted according to the degree of turbidity detected. A sensor system of this kind combined with an appropriately designed dosing device is disclosed, for example, in the publication WO 2011/110243 A1. In addition, the publication WO 2005/058126 A1 discloses a dishwasher incorporating a dosing device for dispensing additives, e.g. into the wash tub of the dishwasher. Here at least one base chemical not used for rinsing and/or at least two base chemicals together, but not all the chemicals of an all-round product together, and/or at least one reaction mixture of base chemicals can be added independently.
However, the existing technology does not allow the dirt load in the rinsing or detergent solution to be adequately characterized, particularly in terms of detecting dirt components particularly relevant to the cleaning process, such as greasy, starchy or protein-containing soilings, particularly in isolation. As the different dirt components also require different constituents of the detergent or cleaning agent used in order to ensure efficient cleaning, it is desirable to provide more specific sensing so that dosing rules in the washing or rinsing process can then be derived therefrom. The lack of such a possibility in existing systems means that the user's desired cleaning outcome is often not achieved.
In addition, the disadvantage of the currently used optical measuring systems which determine the turbidity of the detergent solution/wash water is that they cannot differentiate between turbidity levels caused by dispersed soiling from the wash load, residual dirt from the machine, particularly the machine sump, turbidity levels caused by the detergent used or deposits such as limescale. There is therefore also a need to provide improved optical sensor systems that are able to differentiate between the actual dirt load and other factors affecting the turbidity of the water.